Radio tags or cameras are often used as sensors capable of detecting positions of objects.
Although the radio tags basically never fail to identify the ID of an object (because the ID identification of an object is carried out based upon ID information transmitted by a transmission tag attached to the object to be identified), their position measuring precision is not good in comparison with that of the camera. Moreover, for example, another issue arises in which, since radio waves are absorbed by moisture, the detection of the tag becomes instable. For this reason, under a general environment in which, different from a factory or the like, the environment is not properly prepared, the position measuring precision of the radio tag is not expected so much. In particular, for example, when a person or the like containing much moisture is carrying a radio tag, the positional error might become 1 m or more, or the tag itself might not be detected.
Moreover, in the case of the camera, its position measuring precision is better than that of the radio tag, when the detection of an object is appropriately carried out; however, the object ID identification precision cannot be set to 100% (because the object ID is identified based upon image-based features obtained by the camera (shape, color, or the like)). In particular, the identification rates of objects having similar image-based features become lower. For example, it is very difficult to identify objects having similar colors or shapes, such as a tomato, an apple, and the like, with high precision.
In this manner, since degrees of detection performances are different depending on the respective kinds of sensors, it is difficult to identify an object and also to determine its position by using only one kind of a sensor. Therefore, a technique has been proposed in which a plurality of kinds of sensors are combined with one another, and by integrating pieces of observation information of the plurality of sensors of different kinds, the position of an object is estimated while compensating for their insufficiencies in observation precision of the sensors of the respective kinds (Non-Patent Document 1).